Why use POSIX message queues?

POSIX message queues provide a familiar interface for many realtime programmers. They are similar to the "mailboxes" found in many realtime executives.

There's a fundamental difference between our messages and POSIX message queues. Our messages block—they copy their data directly between the address spaces of the processes sending the messages. POSIX messages queues, on the other hand, implement a store-and-forward design in which the sender need not block and may have many outstanding messages queued. POSIX message queues exist independently of the processes that use them. You would likely use message queues in a design where a number of named queues will be operated on by a variety of processes over time.

For raw performance, POSIX message queues will be slower than QNX Neutrino native messages for transferring data. However, the flexibility of queues may make this small performance penalty worth the cost.